1. Field of the Invention
This invention relates to a figure editing apparatus and, more particularly, to a figure editing apparatus capable of editing a graphical program by using a two-dimensional display.
2. Description of the Prior Art
A conventional figure editing apparatus is available in which figures such as rectangles and circles and character sequences are edited and displayed on a two-dimensional display unit. By using such an apparatus, it is possible to designate editing of individual basic figures. In addition, basic figures can be divided into groups and then editing can be designated for each group.
The operation involved in editing groups is especially effective in moving and copying, and the editing designation itself is simpler than an operation in which the individual basic figures are manipulated one at a time. Another advantage is that the two-dimensional relationship of the individual basic figures can be maintained.
In manipulating groups, it is necessary to designate grouping, cancel the designation, etc., before performing such figure editing operations as the moving, deleting and copying of the figures that have been grouped. In particular, if a designation cannot be made in a rectangular area, it is required that the basic figures be designated one by one.
In a case where a graphical program is to be edited by the above-described figure editing apparatus, the following problems arises:
In general, many programming languages have a structure dictated by the character of the particular language. For example, a program is composed of a collection of statements, and each statement comprises a number of structural elements. Accordingly, in a program to be edited by the editing apparatus, some of the node symbols have a plurality of variable attributes. When a plurality of variable attributes are attached to a node as a character string, it becomes difficult to understand the structure of the program at the display stage and, at the same time, the operations for deleting, moving and copying parts of the program structure entail editing of the character strings. Consequently, operation is troublesome and complicated. On the other hand, if the variable attribute portions are registered as new node symbols, the operation for editing individual attributes is simplified. However, when editing is applied to the entirety of a node having attributes attached thereto, this entails a grouping operation, which is a troublesome task.